Moisture indicators for oxygen-releasing chemical cartridges are preferably used in respiratory protection devices which protect the users of the protection devices as short-term escape or first-aid devices in atmospheres that are unsuitable for breathing. Such devices are packed hermetically together with the chemical cartridge in a carrying container that is opened only shortly before the use of the device. Since the chemical cartridge reacts to moisture and releases oxygen in this reaction, loading of the chemical cartridge with moisture prior to the use of the device must be avoided. To ensure this, a moisture indicator which monitors the atmosphere surrounding the chemical cartridge inside the device and indicates the breakthrough of moisture via a color change is attached to the carrying container. A chemical cartridge previously damaged by moisture can thus be recognized in time and replaced before the use of the device.
A respiratory protection device with a moisture indicator has become known from German Patent Specification No. DE-PS 33,15,070. The respiratory protection device consists of a carrying container with a chemical cartridge based on potassium peroxide, through which the user of the device breathes by pendular breathing. The carbon dioxide exhaled and the moisture present in the breathing air are bound by the chemical cartridge, and oxygen is released during this reaction. Due to the limited amount of oxygen that can be generated from the potassium peroxide cartridge carried by the user, it is important, before the device is used, to hermetically seal the inside of the carrying container against the intrusion of moisture. This is achieved with a circumferential seal along the seam of the carrying container. Furthermore, a moisture indicator, which detects moisture that has penetrated, is provided. Potassium peroxide, whose color changes irreversibly from yellow to colorless on penetration of moisture, is used as the moisture indicator. Damaged chemical cartridges can thus be recognized and replaced in time, so that the user of the device will always carry with him a respiratory protection device with full protective capacity.
It is disadvantageous in the case of the prior-art moisture indicator that the color change is difficult to recognize if the device is used under unfavorable conditions, e.g., underground. In addition, the moisture indicator is insensitive to the intrusion of small amounts of moisture, which may render the chemical cartridge unfit for use especially during prolonged storage. In this case the chemical cartridge is damaged before the color of the moisture indicator changes.